Electric heating apparatus



1. P. SUNDEHLAND.

ELEcTmc HEATING APPAnAws.

APPLICATION FHS!) FEBA 25.1919. 1,304,626. Patented May 27, 19H).

4 SHEETVS-SHEE l.

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l. P` SUNDERLAND.

ELECTRIC HEATING APPARATUS.

APPLICATION FILEDIIIB. 25. 1919.

1,304,626. Patonted May 27, 1919 4 SHEETS-SHEET 2.

@I anni J. P; SUNDERLAND.

ELECTRIC HEATING APPARATUS.4 mmculon mso' rfa. 2s. me.

1,304,626. Patented May 27, 1919.

4 SHEETS-SHEET 3.

l. P. SUNUERLAND.

ELECTRIC HEATING APPARATUS.

Arma/.non mss ri. 25. was.

1,304,626. mmm May 27, 191s 4 SHEETS-SHEET 4.

C man? certain defined limits.

UNITED STATES PATENT OFFICE.

JOHN P. SIJ'NDERLAND, 0F ALBANY, NEW YORK, ASSIGNOR T0 GEORGE G. MILNE, 0F RYE, NEW YORK.

ELECTRIC HEATING APPARATUS.

Specificationof Letters Patent.

183,831. Divided and this application filed February 25, 1919. Serial No. 279,092.

To (illicite/11` it. may concern.:

Be it known that I, Joim 1. SUNDERLAND, a eitzen of the United States, and a resident of Albany, in -the county of Albany and State ot.New York, have invented certain new and` useful Improvements in Electric Heating'ikpparatus, of which the following is a specification,

My invention relates to improvements in electricv heating apparatus and is especially adapted to the heating of rivets, bolt blanks and other articles ot' iron, blass and the like, thc ohmie resistance of which is relatively low' when cold. This application is a divi- ,sion of my prior application Ser. No. 183,831 filed August 1st, 1917.

lt has heretofore been suggested that rivets may be. heated' by passing an electric cur rent therethrough )ut prior arrangements have been unsuccessful because of burning of the rivets. This burning of the. rivet or other article is the local melting or liquefying of the rivet particularly at the end of the rivet. In my prior application Serial No. 247,480 filed July 31. i918, I have described and claimed a method of preventing this burning by keeping the voltage within W'hen the rivet, bar or other article of iron or the like is placed in circuit with the secondary of a suitable transformer, the ohmic resistance of the article is relatively low because it is' cold. Upon heating up its resistance increases, but when first put in circuit it practically short circuits the secondary as the term' short circuit is commonly used. The main ob.-

ject of the present invention is to provide an improved system or apparatus which will keep down the voltage at the start so as to prevent -the How of'excessive current which would cause burnin of the rivet or other articles and which initial burnin is often evidenced by a splattering ofit e molten metal.

Further and more specifieobjects, features i und advantages will more clearly appear from the detailed description given below taken in connection with the accompanying drawings which illustrate an apparatus articularly adapted for heating rivets, olt blanks and the like although with modifica- Figure 1 is a side view Patented May 27, 1919.'

F ig. 5 is aseetion through the trans` former, taken on the line B-B of Fig. 9.;

Fig. 6 is a diagram illustrating diagrammatieally the transformer connections and windings. f 'i Referring to the lvarious figures, l represents a base boardon which is secured an insulating board or sh et` of asbestos 2. Socured upon one endo the base is an electrical contact head of 'soft metal, such as copper, 3, extending along the front of the apparams. Iivoted to the framework at 5 am two pairs of arms 4, in the ends of which are secured respeetively,'electrical Contact heads of soft metal, such as co ipcr6, the heads being insulated from tile arms 4, which support them. Handles 7 are suitably secured to the arms 4, so that the heads 6 may be raised and lowered away from anc toward the head 3 to permit the insertion o rivets 8 between the heads, with one end of each rivet abutting the head 3 and the other end of each rivet abutting one of the heads 6. i Y

-9 represents a transformer, suitably Secured to the base. and having bolted to the top thereof brackets 10, which may serve as handles for the apparatus. The primary' of the transformer consists of three sets of windings 11i, 1Q and 13,'consisting'of 100 together by copper straps 20, the upper end of turn 1G is connected to the lower end of turn 15 by copper straps 21, and the upper end of turn 18 is connected to the lower en of turn 17 by copper straps 22. Bolted between the straps 19 are two sets of copper strap conductors 23 and 24, one-half of the straps 23'being bolted to the underneath side of one of the heads 6,- and the other half of the straps 23 being bolted to the top of the head 6, asclearly indicated in Fig. 1. Likewise, one-half of the straps 24 are bolted to the underneath side of the other head 6, and the other half of straps 24 are bolted to the upper side of the other head 6, so thatJ each head 6 is electrically connected the u er ends of turns 15 and 17 through exiiilz connections. Bolted between the straps 2() are two sets of flexible electric strap conductors 25 and 26, which are similarly bolted to the lower head 3 half being bolted to the underneath side of said head, and half being bolted thereto on the upper ledge of the head, as clearly indicated in Fig. 1.

I also provide. two.extra secondary turns on the transformer, these turns being indicated at 27 and 2S (see Fig. 5). The turn 27 li'es adjacent the turn 15 and is in electric Contact therewith substantially over its whole length. The turn 28 lies ad)acent the turn 16, but is insulated therefrom by insulating material 29. The upper end of turn 27 is electrically connected to the .upper end of turn 2S by copper connecting straps 30. The lower end of turn 27 is connected to the lower end of turn 9.8 by connecting straps 31.

Surrounding the primary and secondary windings is a laminated magnetic structure of soft iron 32, the shape of the laminations being shownI in Fig. 5, In this ligure, the shape of the laminations of the core structur`e 14 is also shown. i

"The ends of the primary turns are brought out from the primary coils to a connection box 33.

Pivoted to a cross-bar 34 (see Fig. 2) lare two sets of arms 35 and 36. Back of the said arms 35 is a wedge-shaped member 37, and back of the arms 36 is a wedge-shaped connected to the upper end of the arms 39 and 40, pivoted at 41 (see Fig. 2) and 00nnec'ted to lever arms 43 and 44, respectivel so that, upon depressin the lever arm 3 or 44, the wedge-shape member connected thereto will be forced between the inner ends of the arm 35 or 36 and cause the outer ends of these arms to approach one another and engage the rivet 8 intermediate its ends,

so as to make an electrical contact with the rivety intermediate its ends.

Bolted between the conducting straps 31 is a set of copper connecting straps 45,

member 38, the members 37 and 38 being' divided into four groups, the outer end of each group being secured to make electrical connection with the inner end of one otA the arms 35 and 36, respectively (scc Figs. 1 and 2).

Any suitable connections 46 may be made to the ends of the lever arms 43 and 44, so that these arms may be depressed to cause the arms 35 and 36 to electrically engage the rivets therebetween, and ikewise any suitable means may be provi ed to cause the arms 43 and 44to Vbe retained in their depressed condition, so that the arms 35 and 36 will continue to engage their respective rivets duringr the heatingthereof.

In operation, the rivets are placed between the heads 3 and 6 and the head 6 lowered thereon so as to hold the rivets therebetween under pressure. In the machine shown, the pressure A1s about eight ounds.

Assuming .the trans ormer to be energized, current then passes from the secondary terminals through the heads 3 and 6 and through the rivet, causing the rivet to be heated :from its -flat end down; that is, it becomes hottest at its flat end and the rivet gradually becomes softened from its Hat end downwardly or toward its head.

I find that the successful heating of rivets by electric currentdepends on maintenance of certain conditions of voltage applied, and ratio between contact resistance and effective impedance in the rivet such as is fopnd in the operation of the apparatus as above described. The heating of the rivet is caused by liberation'of heatl energy due to the opposition to the current. 4This opposition 'may be divided into two classes, that due to the contact resistance between the contact heads and the ends of the rivet and that due to the effective impedance in the rivet which may consist ofohmic resistance, hysteresis losses, eddy current losses, inductance and skin elfect losses. These vary materially with the shape and size of the rivet and the material from which it is made` and the nature of the current employed. In the apparatus described the contact resistance between the contacts and the end? of the rivet is such thatl the upper or fla end of the rivet heats faster than'the shank or middle portion of `the rivet. 1`his appears to be due to a relatively 'large amount of heat liberated at this end at the pointof contact, by the current overcoming the contact resistance. In thsmanner the heat is concentrated where it is needed most so that the final heating of the rivet is accomplished in a minimum time and with a minimum consumption of energy.

However, this is perhaps not the most important feature, because, if the end of the rivet is melted or burned by this so called concentration of heat, it is not suited to be afterward inserted in the hole in the Work because of the damaged end. This vo tage it applied to the very low initial res1stance of the rivet burning of the rivet is the local melting or lquefying of the rivet at theV end of the rivet adjacent the contact. Burned rivets are thrown away as scrap and even by the old methods of heating by coal or oil llame this loss is very large. I have found, however, that by using a relatively low voltage this burning of vrivets: can be entirely eliminated without material loss intime in com-- ple-ting the. heating of the rivets. VIf en excessive voltage is used, so much heat is generated at the Contact that. it can not be conducted into the body may use en applied voltage of about 2 volts or slightly less. However, the highest voltage which jill not burn depends not only upon the size, shape and material of the rivet, and nature of the'current but also upon the slpecd with which the contact. heads conduct tie heatV away' from' the end of the rrivet and the pressure applied. I find, however. thatf according to the preferred form of the in "ention it is best to below six volts.

But even though arelativcly low voltage be applied, sutlicient'to prevent burning durin the `major portion of the heating, such at the start. might, due

or bar, when cold, cause an excessive current to flow ini v'ally which would cause burning or splattering of molten metal at thebcgixr ning of the heating operation. To overcpme this l piovide an apparatus with a markedly drooping cliamcteristic` so that if excessive current tends to flow due to the practical short circuiting of the secondary,tl1e voltage willbe reduced to a point where such spinttering or burning is substantially eliminated. As the rivet or .bar becomes heated and its ohmic resistance increases the applied voltage will automatically increase in order that. th article may be heated quickly, butl the voltage at all times being kept below that which would cause burning.

TheV apparatus as a whole may be given a markedly drooping characteristic many ways as will be apparent to those skilled in the art, but I prefer to do it by provid-` ing the transformer, which is substantially iron clad and hasV a substantially complete iron magnetic circuit for eiiiciency, with a gap or gaps 60 in the magnetic circuit. In the arrangement the gaps G0 comprise air spaces lilled 'with shellac. It will be under stood that by suitable adjustment'of conditions"the effective internal impedance in the rivet and the contact resistances may be such that all parts of the rivet will heut up equally fast or Ithe center will heat up fastest,Y but the heating of the end fastest of the rivet fast enough to prevent local overheating andy being an especiallymportant factor in pres-v ent day' commercial operations.

If a, long rivet is being heated, it 1s desirable to make use of the third contact device v or devices 35 and 36, in which case lever arm 43 is depressed, causing extra current, generated in the secondary turns 27 and 28,140 be passed through the upper end portion of the rivet, so as to morequickly heat that portion of the rivet, which is desired toghe heat/ed and without burning the rivm-that is, causing it to become too soft at theend that is to be upset late. p

Suitable switching Vapparatus is provided as shown in Fig. 6,` whereby the number o turns of primaiwindings may be varied, that is, some o the turns may be cut out. F or that purpose, a switch 50 is provided, adapted to multe all 300 turns are When the switch is thrown to contact 52, only 27 5 turns wilLbe in circuit, and. when thrown to Contact 53, only in circuit, the supply mains being connected, one to the switch 5() and the other to contact-5543iy V l, A Y; l

In thc apparatus particularly illustrated in the drawings, I prefer to apply 220 volts at G0 cycles across the transformer so wound 'that about 3 amperes will flow in the primary when they secondary is open-circuited..

`It will be noted that the four main secondaryV turns are connected inY pairsf-two pairs in parallel, and two pairs inseries.

When heating rivets i inch in diameter by 1 inch long I refer-ably u the 300 turns of primary win in and when so connected the calculated vo tege on the secondary with the secondary opcn-circuited volts.

\Vith rivets long, I preferably mary turns, so es to use turns, thus producing a. calc ated open-cu'- cuit secondary voltage bf about 1 .6 volts.

When heating rivets 2% inches long, I pref rably use about 200 turns in the rimary and a calculated opencircut secon ary voltage of about 2 volts.

If e i inch diameter 3 inches long rivet is beingheated, I pre erably increase the open-circuit secondary voltage to about 2.5 volts, and if' ai inch diameter by 4% inches long rivet is being heated, I preferably ininch" diameter by ig'inches cut out part of the pricontact withcontact 51, if i desired to be in circuit.

200 -turns will be is about 1.4

inch in diameter by i the primary and to have onl 275 primary crease the calculated secondary voltage to be used Without, burning the rivets or bo t blanks I preferably keep the applied voltage during heating under about -,t or G volts. Thus` the transformer should be so designed and wound or the source of electric current be so selected and connected as to send a current through the heads and rivet 0f such size as to heat the rivet soft the required distance without burning the end of the rivet.

lVith the above apparatus, I am enabled to heat rivets in from 3 to 60 seconds without burning. i

lVhile I prefer to use alternating current as energizing means, certain of my improvements may be found advantageous in case a direct current is used.

It is not necessary, to the broader aspects of ni invention,I that the apparatus be provide( with two heads (i, but I find that if a plurality of heads 6, with coperating head or heads 3, is provided, supplied from the same source or transformer, and in parallel a plurality of rivets may be heatcd'simultaueously. I find that', even although such plurality of rivets may be inserted simultaneously, one will always become heated before' the other, so that the operator may insert and remove the rivets alternately, and thus greatly increase the speed with which rivets may be heated by the apparatus.

As shown in the drawings, only one head 3 is provided, but this is equivalent to two heads, as one portion copeiates with one head 6 and the other portion coperaties with the other head 6.

Since the third contact device 35 is connected to secondar windings on the transformer, which emiirace only two turns in' parallel, the voltage applied between the contact devices 35 and 36 and the head 6 will be about half of the voltage applied between the heads 6 and 3.

It will be noted 'that the other or upper terminal of the secondary windings 27 and 28 are common with the upper terminal of the windin 15 and connections 23.

While I ave described my improvements in great detail and in respect to anapparatus for carryin them out in one form, I do not desire to e limited to such details, since many changes and modifications may be made and the invention embodied in widely dilfering forms without departing from the s irit and scope of the invention Yin its broa er aspects. I desire to Coverall forms and methods coming within the language of the appended claims.

What I claim is v,

1. An apparatus of the class described having in combination acontact adapted to make contact with the flat end of a. rivet, bar or other article, a second contact ,adapt4 ed to make contact with the rivet, bar or similar article, and a transformer having a low potential secondary with its terminals connected to said contacts respectively, said transformer having a substantially complete iron magnetic circuit (but with a, gap

or gaps therein) to give the transformer a markedly drooping,r characteristic to prevent the fiow of excessive current when the rivet. bar or other article is first placed in f circuit.

An apparatus of the class described having in combination a contact adapted to make contact with the dat end of a rivet, bar or other article, a second contact adapt ed to make contact with the rivet, bar or similar article, and a transformer having a low potential secondary with its terminals connected to said contacts respectively, said transformer having a substantially completeiron magnetic circuit and a markedly drooping characteristic to prevent the How of excessive current through the rivet, bar or other article. 85

3. An apparatus of the class described having in combination a contact with a dat face adapted to make contact with-the dat end of a rivet, bar or other article, a second contact adapted to make contact with vthe rivet, bar or similar article, and a transformer with its secondary connected to said contacts respectively, the apparatus having a markedly drooping characteristic to prevent the tiow of excessive current when the impedance of the rivet, bar or other article is relatively low.

-L An apparatus of the class described having in combination a contact of relatively soft metal with a Hat face adapted to make contact with the fiat end 0f a rivet, bar or other article, a second. cpntact adapted'to make contact with the rivet, bar or similar article, and a transformer with its secondary connected to said contacts respectively, saidttransformer having a substantially closed iron magnetic circuit and the apparatus having a markedly drooping characteristic to prevent the flow of excessive current when the rivet, bar or other article is first placed in circuit.

5. In an electric heating apparatus of the class described, the combination of two electrical contact heads, one of which is movable with respect to the other, and a transformer havin its secondary connectedto said heads, said transformer having a relatively short gap or gaps in its vmagnetic path to prevent an excessive current when the secondary is substantially short circuited.

6. The vcombination oftwo contacts for making electrical connections with rivets, bars or other articles, and a. transformer with its secondary terminals connected to 126 .said contacts respectively, the Vapparatus having a markedly drooping characteristic to prevent the How of excessive current throu h the rivets, bars or other articles.

7. n apparatus of the class described 130 `trical contact with the having in combination two contacts for making electrical connections with a rivet, bar or other article, and a transformer with its secondaryv terminals connected to said contacts respectively, said transformer hav ing a substantially complete iron magnetic circuit and the apparatus having a markedly drooping characteristic to Prevent the flow of excessive current when the rivet, har

or other article is first placed in circuit.

8. The combination of two contacts for making electrical connections with rivets,bars o1 other articles, and a transformer with its secondary terminals connected to said con tacts respectively, said transformer having a substantially complete iron magnetic circuit but with a gap or gaps therein to give the apparatus a markedly drooping charactieristic to prevent the fiow of excessive current when the rivets, bars or other articles are first placed in circuit.

9. An apparatus of the class described having in combination two contacts for making electrical connections with a rivet, bar or other article, and a .substantially iron clad transformer' with its secondary terminals connected to said contacts respectively, said apparatus having a markedly,v drooping characteristic to irevent the flow of excessive current when tlhe rivet, har or other article is first placed in circuit.

10. An apparatus of the class described having in combination a Contact with a fiat face adapted to make electrical contact with the end of a ibar, rivet or other article, a. second contact also ada ted to make elecar, rivet or other article, and a substantially iron clad transformer, having a substantially complete iron magnetic circuit, with its low potential sec- 40 11. An apparatus of the class described i having in combination a transformer, a plurality of contacts for making electrical connections with a plurality of rivets, bars or other articles respectively to connect the rivets bars or other articles to the transformer terminals, but with the rivets, bars or other articles in parallel with one another, said apparatus having a markedly drooping characteristic to )revent the flow of excessive current through the rivets, bars or other articles when their impedance is relatively low. V

12. An apparatus of the class described having in combination, a transformer, means for electrically connecting the transformer to a bar, rivet or other article to heat the same, said means including an electric contact device for gripping the bar or other article intermediate its ends, and said apparatus having a markedly drooping characteristic to prevent the fiow of excessive current through the rivet, *bar or other .article when it is first laced in circuit.

Signed' at Al any, in the county of Alhanv and State of New York, this 20th day of Feb., 1919.

JOHN I. SUNDERLAND. Witnesses:

WALTER L. MJLLER, HAnoLD E. DE Von. 

